Various kinds of information may be presented in a digital content format, including audio, video, text, images and multimedia information. Digital content may be rendered by hardware playback devices and by computer systems operating software playback programs. Hardware playback devices typically are small, lightweight devices having a special purpose processor that renders the digital content stored in memory into audio output or visual output, or both. Software playback programs typically control the output functionality of a computer system to render digital content.
The convergence of technological advances in the compression, storage and transmission of digital data has resulted in a global communications network that allows digital content to be distributed rapidly to a large number of potential customers. At the same time, this technological convergence has enabled unprecedented quantities of digital content to be copied flawlessly and distributed to a large number of people. For example, users easily may exchange unprotected digital files by electronic mail or by direct file transfer over the Internet. Users also may access and download digital content posted on a web page using a conventional web browser application program executing on a computer system.
Digital content owners understandably are concerned about the potential theft and loss of control over the distribution of their works by and between unlicensed users. Cryptographic techniques have been developed to control the distribution of digital content. For example, digital content may be encrypted, and the encrypted content and a decryption key may be transmitted to licensed users. Licensed users may use the decryption key to access the encrypted digital content. External devices (e.g., tokens or dongles) also have been used to control the distribution of digital content. For example, a token or dongle may be required to be connected to a computer or other playback device before a licensed user may access the protected digital content. Still other systems and methods for controlling the distribution of digital content have been developed.